Optometry Pro

HAPPY NEW YEAR

2015-12-31T21:23:00.000-08:00

Wish u a Happy New Year

One of wishes on my Bucket List for the year 2016 is to enter 1 post a day (excluding Sundays).
That's almost 300 Posts, I pray to god that what i do may become useful to fellow optometrist. The name of the Editor will remain anonymous because the data i am going to release here could make some serious (may be small) ripples through out the Optometry Community.

There will not be any copy/past content on here, because i want to take this serious. I received many email from around the Globe. Most of the matters are related to continuing education for working Optometrist CET.

New Writers Wanted
I therefore will focus on those matter, also since i cannot carry this burden of CET alone, I want some good optometry writers for this blog. i will add give you credit for your articles as some of you may wish.Please avoid copy/paste contents
we crossed 19 thousand visitors today, which for me is a big deal.

About Revenue/Adds
as you noticed i am not making a penny with this blog through Add programs or other means of income, that's why it will still remain on Blogspot, and that's why i wont be able to pay anything if you choose to write for OPTOMETRYPRO.
But if some company's decide to contribute to this Blog, you are most welcome on this matter.

Keratoconus

2015-10-03T07:28:00.000-07:00

Definition
Corneal Disorder characterised by the protrusion of central corneal associated with apical thinning and progressive myopia with irregular astigmatism

Clinical Characteristics
Blurred vision that cannot be fully corrected by glasses
Increasing Astigmatism
Glare and monocular diplopia
Sudden decrease in Vision, pain and photo phobia may occur in acute corneal hydrope

CL for Keratoconus management

Options for Keratoconus include:-
Spectacles
Soft Contact lens
Hybrid Contact Lens
INTACS
CXL
Keratoplasty
Ross-K lenses
Nissel K2
Rigid Lenses
Kerasoft ICL
Scleral CL

RGP lenses for Keratoconus
OLD RGP matterials (PMMA) was usually discomfort for Pt
RGP2 as a spherical lens is a better option because of better oxygen transmission to cornea

RGP fitting
usually done from a trial set or ordered from Keratometry reading , along with spectacle refraction and back vertex power (BVD)

The total lens diameter(TD) may be around 9:50mm with the

Low Vision

2015-10-03T04:29:00.000-07:00

Definition
Impairment of vision which causes restriciton to everyday life and which cannot be corrected by conventional spectacles, cl or medical intervention

History
General ( what are their concerns )

Ametropia

2015-10-03T00:12:00.000-07:00

Definition
Optical condition of the eye in which the incident parallel rays of light do not come to focus upon the sensitive layers of retina,with accommodation at rest is known as Ametropia

Refractive surgeries

2015-09-19T02:22:00.001-07:00

Definition
Any procedure used to correct the refractive error

Myopia (short-sightedness)
the refractive power of the eye must be decreased either by flattening the cornea or by IOL insertion of appropriate power

Hypermetropia ( Long sightedness )
making the shape of the cornea to be steeper or an appropriate IOL lens is inserted

Astigmatism (refractive power is not same in all meridian )
Cornea must be flatter in the axis where the refractive capacity of the eye is relatively greater or steepened the axis where it is relatively weak or Toric IOL can be used

Presbyopia(reduction of near vision with old age)
Multi focal IOL can be used
Mono vision
Where one eye is corrected for DV ( made emmetropic) other eye is made or left -1.50 D myopic to allow the eye to focus on near objects

Corneal refractive Surgeries
Corneal ablation by excimer laser

LASIK Laser assisted stromal in-situ keratomilesis)
Epi-LASIK    (epithelial laser - assisted in-situ keratomilueisi)
PRK    Photo refractive Keratoconus
LASEK             (laser- assisted sub epithelial Keratomiluesis)

Basics of Spherical Aberration

2015-09-19T02:11:00.000-07:00

Definition:An Aberration is a distortion of an image of an object that is caused when rays of light dont exactly obey the laws describing perfect optical systems

Main Aberrations can be described as
1    Spherical aberration
2    Chromatic Aberration
3    Oblique Aberration
4    Coma
5    High order Aberration

Correction of spherical Aberration in order to enhance vision quality
Correction of High order Aberration has been prime importance in Corneal refractive surgery

Spherical Aberration
Caused by the shape of the refractive surface and magnified effects
eyes with a dilated pupil is a significant problem

Positive Spherical Aberrations

Light rays entering the eye near the pupil edge are focused in front of the retina

Negative Spherical aberration

Light rays entering through the centrally and focusing behind the retina

Abbreviations of a case history.

2015-08-20T03:06:00.004-07:00

Abbreviations that could be used during the recording of a case history

Px (or Pt) Patient

OK Okay

Rx Prescription/spectacles

Sxs Symptoms

CC or PC Chief complaint or Presenting complaint

OH Ocular history

RFV Reason for visit FOH Family ocular history

DV Distance vision FMH Family medical history

NV Near vision GH General health

R Right

BP Blood pressure

L Left

RE (or OD) Right eye

LE (or OS) Left eye

IDDM Insulin-dependent

NIDDM non-insulin-dependent diabetes mellitus

B (or binoc) Binocular

meds Medication

BE (or OU) Both eyes

Ung. Ointment

c –(or c) With

o.d. Once daily
s– (or s) Without b.i.d.
(or b.d.) Twice a day
1/7, 3/7 1 day, 3 days
t.i.d. Three times a day
H Horizontal q.h. Every hour
V Vertical LEE Last eye examination
H/as Headaches
LME Last medical examination
q Increase
F & F Fit and fashion (of spectacles)
p Decrease

CLs Contact lenses

Follow us on Twitter @optometrypro

2015-08-18T04:23:00.001-07:00

Hello Fellow Optometrist , We have Joined Optometry PRO on Twitter, you can follow us there @optometrypro for new posts, discussions and all things Optometry with our editors

https://twitter.com/optometrypro

Best Book to Refer before attending Dubai Health optometry Licence Assesment

2014-10-20T03:06:00.003-07:00

If you are going to Attend DHA Optometry Licence Assesment examination .Pls read & study this book completely. This link may work .

How to register for Dubai Health Care Professional License - Tutorial - كيفية التقديم على تراخيص ا...

2014-06-15T15:28:00.001-07:00

AC angle & depth assessment with Pen torch

2014-04-01T00:06:00.000-07:00

Assessment of the anterior chamber angle (ACA) and ant erior chamber depth (ACD) is necessary for several reasons. Many types of glaucoma require ACA assessment for a correct diagnosis eg, narrow angle glaucoma, angle closure glaucoma, pigmentary glaucoma and neovascular (or 100- day) glaucoma. Visualisation of the angle is also recommended where there is any suspicion of peripheral anterior synechiae, angle recession or iridodialysis post-trauma. It is also useful for establishing the patency of peripheral iridotomies and a patient’s suitability for anterior chamber implants. In everyday practice it is useful to know the width of the angle to help determine the potential risk of angle closure prior to carrying out pupil dilation on a patient. This article describes the pentorch methods that can be used to assess the ACA and/or ACD in clinical practice.

Pen torch method

The simplest method of assessing ACD is by shining a pen torch into the patient’s eye from the temporal canthus such that the pen torch lies in the same plane as the eye. In the case of a deep anterior chamber, the iris lies flat and the whole iris will be illuminated. In the case of a very shallow anterior chamber the iris lies forward, blocking some of the light and very little of the iris is illuminated. Based on the amount of eye illuminated the ACD can be graded

Important Preoperative Assessments

2014-03-31T04:42:00.000-07:00

Preoperative astigmatism (regular or irregular) has to be considered when planning cataract, corneal or refractive surgery. In the case of physiological astigmatism we can plan a neutral effect or we can try to limit the effect of the induction of astigmatism the surgical procedure planned, or use it to our benefit.

Important Preoperative Assessments

Important measures in the preoperative evaluation are: unaided and aided visual acuity, autorefraction, manifest and cycloplegic refractions, keratometry, computerized corneal topography and endothelial cell count.

Endothelial changes should be assessed, since Fuchs’ endothelial dystrophy, traumatic breaks in Descemet’s membrane, and other causes of endothelial dysfunction may preclude stromal ablation.

Pupil size measured in different degrees of illumination is essential. Young patients with large pupils should be advised of potential glare, halo and night driving problems following refractive surgery. One has to weigh the benefits versus these difficulties in highly myopic patients requiring small optic zones to correct that much myopia. In patients with myopia over –10 D and large pupils, refractive surgery may give rise to visual discomfort. The same applies to phakic IOL implantation when using very thin, foldable lenses with a small diameter optic.

Biomicroscopy

The presence and quality of the tear film should be evaluated and specific tests, such as Schirmer’s and tear film breakup time (BUT) done. Corneal clarity, and absence of conjunctival pathology which could perhaps cause difficulty with fixation of the suction ring in LASIK, should be noted. Tonometry is necessary to exclude undiagnosed ocular hypertension or glaucoma and to establish a preoperative intraocular pressure (IOP) level.

The examination of the anterior segment for lens changes, such as early posterior subcapsular cataract, should be done both to document its existence prior to surgery from a medical/legal point of view, and to suggest the possibility of lens extraction

by phacoemulsification, with (or without) implantation of an intraocular lens (IOL), as an alternative method of refractive correction.

Detection of Corneal Problems

One of the most important principles of laser ablation with the excimer laser is that the currentinstruments, will superimpose the ablation on any irregularity present at the time of surgery. The two most common sources of preoperative irregularity are warpage from rigid or gas-permeable lenses. Even soft lenses can produce limited warpage in some patients. If the topography shows significant irregularity or an abnormal pattern (for example steeping of the topography of the inferior cornea relative to the superior), we continue to monitor the topography at one- to two-month intervals until the topography is normal and stable.

Some irregular astigmatism may occasionally be noted during examination. The same strategy of following the corneal topography over time should be used. However, it is very rare that soft contact lens-induced warpage would take more than one to two months to resolve.

Keratoconus patients are frequently detected in a busy kerato-refractive practice. Studies have shown that two to 10 percent of the patients who are seen for preoperative screening will have inferior steepening of the corneal topography consistent with the patient being a keratoconus suspect or having frank keratoconus. This very high incidence is due to self-selection. These patients are typically not satisfied with their quality of vision with glasses or contact lens.

Dry Eye Patients

A major problem following LASIK is the reduction in tearing that is attributable to the corneal nerves being severed during production of the flap. This interrupts the normal cornea-central nervous system-lacrimal gland reflex arc that modulates even basal tear production. It also temporarily interrupts the known neurotrophic effect of the corneal nerves on the epithelium. Patients with manifest dry eye will be even more likely to have major symptoms and signs after surgery. Usually, these patients do get better over time, but they often need to use frequent tears and ointments without preservatives to get through those first few months.

Ophthalmic Ultrasound - Introduction

2013-06-13T19:33:00.000-07:00

We live and practice ophthalmology in an era of sophisticated imaging techniques: computed tomographic (CT) scanning and CT angiography, magnetic resonance (MR) imaging and MR angiography, and digital subtraction angiography. All of these procedures can be helpful to the physician dealing with ocular and orbital disease, but none is more useful than ophthalmic ultrasound , It is the only method of determining the optimum intraocular lens power for a patient about to undergo cataract surgery, it provides an accurate representation of tissue status in patients with opaque media, and it is crucial in the investigation of patients with clinical evidence of orbital disease.

In my opinion, it is the most sensitive test for thyroid eye disease, it can often provide a tissue-specific diagnosis of an orbital mass, and it can accurately assess the diameter of the optic nerve and provide evidence of whether enlargement of the nerve is caused by a solid process or surrounding fluid. the technique is extremely operator dependent. One cannot evaluate the results of a B-scan (let alone an A-scan!) as one does a CT scan or MR image. The key is having a superb, experienced ultrasonographer .ophthalmic ultrasound remains an integral part of ophthalmology practices around the world. Its role continues to be in the diagnosis and management of a wide variety of ocular and orbital disorders. Understanding both diseased and healthy ocular structures, as well as mastering the prescribed examination techniques, remains an essential task for echographers, no matter what their level of expertise may be.

What is PTK & PRK treatments ?

2013-05-20T14:26:00.000-07:00

The concept behind PTK (phototherapeutic keratectomy)
is to use the excimer laser to remove superficial corneal opacities and/or to smooth the corneal surfaceThe excimer laser has been used since the late 1980s to reshape the anterior corneal curvature in a procedure known as photorefractive keratectomy (PRK).Not many Doc prefer this treatment but i have assisted in one of the treatment personally

Initially for myopia and later for astigmatism and hyperopia.The concept behind PTK is to use the excimer laser to remove superficial corneal opacities and/or to smooth the corneal surface.
In this surgery, the epithelium is removed and the laser is applied to ablate a specific amount of Bowman’s membrane and stroma. The excimer laser can also be used to remove superficial corneal pathology in a procedure termed phototherapeutic keratectomy (PTK). Unlike PRK and PTK, laser-assisted in-situ keratomileusis (LASIK) is a procedure where a thin flap of corneal tissue, including epithelium, Bowman’s membrane, and stroma, is fash fashioned, and the excimer laser is used to reshape the stroma under the hinged flap. Afterward the flap is repositioned on the corneal surface without sutures.The excimer laser clinically used in ophthalmology utilizes 193-nm wavelength ultraviolet light to break molecular bonds in the cornea to remove tiny amounts of tissue. One pulse of excimer laser light removes approximately 0.25 µm of tissue, depending on the specific laser system.

The concept behind PTK is to use the excimer laser to remove superficial corneal opacities and/or to smooth the corneal surface. This procedure is potentially applicable to a large number of patients, including those with anterior corneal dystrophies, anterior corneal scars, and superficial corneal irregularities. Over the past 7 years, we have learned a great deal about when excimer laser PTK is effective and when it is not.
Excimer laser PTK is procedure to treat anterior corneal pathology affecting visual function, including symptoms of pain and/or decreased vision. It is specifically indicated for conditions such as anterior corneal dystrophies, including anterior basement membrane dystrophy, dystrophies of Bowman’s membrane, and granular and lattice dystrophies. It is also approved to treat anterior stromal scars occurring after corneal ulcers, ethylenediaminetetraacetic acid (EDTA) chelation of band keratopathy, trauma, or surgery (eg, pterygium surgery). Elevated lesions, such as Salzmann’s nodular degeneration, can also be treated but are often more easily and effectively improved with superficial keratectomy. FDA indications state that the bulk of the pathology should be in the anterior 33% of the cornea. Additionally, not more than one third of the cornea should be removed and at least 250 µm of tissue should remain at the end of surgery.
Consequently, contraindications to PTK include patients with deep corneal pathology or thin corneas. Caution should be taken in patients with potential healing abnormalities such as patients with keratitis sicca, neurotrophic corneas (eg, after herpes simplex or herpes zoster keratitis), exposure keratopathy, collagen vascular disorders (eg, rheumatoid arthritis), and diabetes mellitus. Eyes with a history of herpes simplex keratitis are at risk for recurrence of herpes after PTK.
Generally, the best candidates for excimer laser PTK are patients with corneal opacities in the anterior 10% to 20% of the cornea without significant irregularity or thinning. Eyes with localized elevated lesions are also good candidates for this procedure. Complications of PTK include infectious keratitis, corneal haze, and corneal scarring. In addition, opacities and dystrophies can recur after PTK, and induced refractive error, most typically hyperopia, but also myopia and astigmatism, is common.
While one of the goals of the procedure is to decrease corneal irregularity, it is not unusual for PTK to cause worsened irregular astigmatism. Patients should understand that PTK is often being performed in lieu of a more invasive procedure such as lamellar or penetrating keratoplasty. Occasionally, PTK is unsuccessful and corneal grafting is required to improve vision.
PTK PROCEDURE
The exact procedure used to perform PTK depends greatly on the specific corneal pathology being treated. There are three general techniques employed to treat most corneas.
The three approaches are used to treat
(1) relatively smooth central anterior stromal opacities (eg,Reis-Bücklers’ or granular dystrophies),
(2) elevatedcorneal lesions (eg, Salzmann’s nodular degeneration),and
(3) recurrent erosions, most commonly associatedwith anterior basement membrane dystrophy.
Often, more than one of these techniques is used in an eye.
PTK for Stromal Opacities
Eyes with anterior stromal opacities, such as corneal dystrophies of Bowman’s membrane (eg, Reis-Bücklers’ dystrophy) and anterior stromal dystrophies (eg, lattice and granular dystrophies, recurrent dystrophies in a graft), generally respond well to PTK. In most of these cases, the epithelial layer is relatively smooth. Often the superficial stromal opacities extend anteriorly into the posterior aspect of the epithelium. In these cases, the epithelium acts as a smoothing or masking agent. Here, removing the epithelium manually actually creates a more irregular surface in many eyes. Therefore, the epithelium is preferably removed with the excimer laser. Laser epithelial removal potentially creates as smooth a surface in the stroma as existed in the epithelium. A large-diameter ablation zone (eg, 6 to 7 mm) is centered over the entrance pupil, and the ablation is performed through the epithelium and Bowman’s membrane and into the stroma.
Preoperatively, an estimate of the depth of the pathology needs to be determined, typically using a combination of slit-lamp biomicroscopy and ultrasound pachymetry. Only a percentage of this depth (eg, 50% to 75%) should be programmed into the laser system computer for initial delivery. When this amount of ablation has been performed, the patient is brought to a slit lamp and examined. Generally, more ablation is then required to remove the majority of the corneal pathology to improve the patient's symptoms. Not all of the opacity needs to be removed to significantly improve vision. This “ablate and check” technique is essential to remove only the amount of opacity necessary to improve symptoms, but not any additional tissue, which would increase the risks of significant refractive change and corneal haze or scar.
PTK for Elevated Lesions Elevated opacities,
most commonly Salzmann’s nodular degeneration lesions and keratoconus nodules, are often treatable with mechanical superficial keratectomy using a blade. Those lesions not amenable to removal with a blade, generally because of some stromal involvement, can be treated with PTK. In these eyes, the epithelium is removed manually only from the elevated portion of the lesion and left in place adjacent to the lesion. A small-diameter ablation zone (eg, 1 to 2 mm) is used to “shave” down the lesion. Ideally, the lesion is ablated to the level of the surrounding stroma, resulting in a smooth cornea. When there are areas of cornea that do not require ablation in close proximity to more elevated areas, the areas not requiring ablation can be coated with a masking agent to protect them. Different viscosities of masking agents can be employed for different lesions. Most surgeons use a variety of thinner viscosity and thicker viscosity preservative- free tears as masking agents. Once the elevated area is relatively smooth, a larger-diameter ablation zone (eg, 4 to 6 mm) can be used to smooth the entire area.
PTK in Thin Corneas When corneal opacities associated with corneal thinning (eg, corneal ulcer scars) are being treated, it is difficult to create a smooth corneal surface without causing a large area of significant corneal thinning. Masking agents are often necessary to produce even a somewhat smooth surface. When required, such lesions can be treated, but the resulting corneal flattening, which can be dramatic, must then be managed, often with a rigid gas permeable contact lens.
PTK for Recurrent Erosions
The third technique is used to treat recurrent erosions, most commonly associated with anterior basement membrane dystrophy. Most eyes with recurrent erosions can be managed with medical therapy such as lubrication,hypertonic agents, and bandage soft contact lenses. With failure of medical management, surgical options are available, including anterior stromal puncture, diamond burr polishing of Bowman’s membrane, and excimer laser PTK. When PTK is used, the entire area of loose epithelium is removed, and the cornea is treated to ablate 5 to 6 µm of Bowman’s membrane. Care should be taken to remove all areas of loose epithelium and then to treat all of the exposed Bowman’s membrane to prevent recurrences outside the treated area.
PTK-Induced Refractive Error
One of the most frustrating aspects of PTK surgery is induced refractive error. Most of the time ablations are performed centrally, causing central corneal thinning and flattening, resulting in induced hyperopia. When peripheral ablations are performed, induced myopia may occur. Induced astigmatism is not uncommon, because corneal opacities are often not uniform and are difficult to completely smooth out with current techniques, even with the use of masking agents. During the early PTK experience, hyperopic shifts of 5 to 15 D were routinely induced.15-19 As more procedures were performed and patients were followed for longer periods of time, surgeons realized that deep ablations were responsible for this hyperopic shift. Techniques were developed, including the “ablate and check” procedure discussed earlier, to combat this adverse effect. Additionally, an antihyperopia ablation was proposed to decrease corneal flattening and induced hyperopia. The effectiveness of these modalities is uncertain. One problem is that precisely how much tissue needs to be removed in any given patient is not known preoperatively. Also, exactly how much hyperopia is induced per amount of tissue removed during PTK is unknown, as is the best method to counteract induced hyperopia.

Slit lamp examination methods

2013-05-20T02:23:00.000-07:00

Bio microscopy of the living eye is a routine ophthalmology examination. The slit lamp enables the user to inspect individual eye segments in quick succession to obtain a general impression of the eye and make a diagnosis. Learn how to do slit-lamp examination in general way.

In a slit lamp, the most important type of illumination is the optical section. All other techniques are variations. For survey examination of the anterior segment the slit is adjusted to full aperture.
This results in a circular, very bright and evenly illuminated field that is slightly smaller than the microscope's field of view. By placing a ground glass into the optical path the entire field of view is illuminated. It is well known that the structure of transparent objects such as the cornea, anterior chamber, eye lens, and vitreous body can only be seen poorly in transmitted or reflected light, as the relative amplitude modulation of light is too weak and the phase modulation is not perceived by the eye. However, such objects can generally be observed well in scattered or fluorescent light.
The basic methods of examination can be classified by the following illumination techniques.
to be continue

Keratometry FAQ

2012-02-21T00:34:00.000-08:00

Here is some of the most Frequently asked questions in matters relating to Keratometry, if you are doing A Scan biometry , these hints will come in Handy
Try to answer each questions & try to think about it for a minute

How much of the cornea is measured with a keratometer?
Why dose a keratometer use doubling of its images?
How should you proceed with the patient’s care?
What if a postoperative patient has a refraction of +2.00 /-2.00 x 90? Where should you cut the suture?
What measurements are necessary in determining the intraocular lens implant calculation?
How does an error in keratometry readings affect the intraocular lens calculation?
What does SRK stand for? What is it ?
Name an easy way to decrease the chance of making an errors in axial length measurement?

How much of the cornea is measured with a keratometer?
Only the central 3 mm, a peripheral corneal scar or defect may be missed by using a keratometer instead of a corneal map.

Why dose a keratometer use doubling of its images?
To avoid the problems of eye movement in determining an accurate measurement. Doubling is done with prisms.
After cataract surgery, a patient has the following refraction: +1.00 /+3.00 x 100. Does the patient have with the rule or against the rule astigmatism?
With the rule astigmatism is corrected with a plus cylinder at 90° (± 15-20°). Against the rule astigmatism is corrected with a plus cylinder at 180° (± 15 – 20°). The patient has with the rule astigmatism.

How should you proceed with the patient’s care?
Check the remaining sutures. Cutting the 11.0 suture will relax the wound and decrease the amount of astigmatism.

What if a postoperative patient has a refraction of +2.00 /-2.00 x 90? Where should you cut the suture?
Changing the refraction to plus cylinder form, you see that the patient is Plano +2.00 x 180 and has against the rule astigmatism. You cannot cut any sutures to relax the astigmatism. The only option is to do a relaxing incision of the cornea, but it is likely that the patient will tolerate glasses, especially if the refraction is close to the preoperative correction. Also, check the preoperative keratometry. The patient may have had against the rule astigmatism before surgery.

What measurements are necessary in determining the intraocular lens implant calculation?
Axial length in millimeters and keratometry readings in diopters. The desired postoperative refraction is also necessary. The SRK formula is commonly used. For emmetropia, the formula is P=A-2.5 (axial length) –0.9(Average K reading), where P equals the implant power, A is the implant constants as determined by the manufacturer, and K is the average of the keratometry readings. The A constant also can be individualized by analysis of previous cases. For each diopter of desired ametropia, add 1.25 to1.50 D. For example, if the SRK formula reveals a calculation of + 18.) D for emmetropia, implant a + 19.50D lens for –1.00D.

How does an axial error that is incorrect by 0.1 mm affect the intraocular lens calculation?
For every 0.1 mm error, the calculation is impacted by 0.25 D. Recheck the A scan if the axial length is less than 22 mm or more than 25 mm or if there is more than a 0.3mm difference in the measurement between the two eyes.

How does an error in keratometry readings affect the intraocular lens calculation?
For every error of 0.25 D, the calculation is is error by 0.25 D. Recheck the Keratometer measurements if the average corneal power is less than 40D or more than 47 D. Also check if there is a difference of more than 1 D in the average keratometer readings between eyes.

Discuss the types of formula in common use for calculation of intraocular power. Give an elense xample of each type.
Ø Theortic formulas are derived from optical priniciples and use assumes dimensions for certain parts of the eye (eg,binkhorst, colenbrander).

Ø Empiric formulas are derived by regression analysis from clinical results. A mathematical relationship between corneal curvature, axial length, and intraocular lens power can be derived (eg,SRK).

What does SRK stand for? What is it ?
The SRK (saunders, retzlaff, and kraff) formula is:
P= A-2.5 L-0.9K
Where P is the power for emmetropia, A is a lens constant, L is the axial length in millimetres, and K is the average corneal curvature in dioptres. The lens constant is an unique constant related to lens type and manufacture . it can be personalized by analysis of results with that lens

Using the SRK formula, how much of an error in intraocular lens power would result from a 0.5 D mistake during keratometry? From a 0.5 mm mistake during axial length masurement?
0.5 D error in keratometry
0.5 x 0.9 = 0.45 D, or about a half a diapter
0.5mm error in axial length
0.5 x 2.5 = 1.25 D
It should be obvious that small errors in axial length can translate into large errors in calculated lens power.

A patient presents with average keratometry readings of 43 D and an axial length of 19mm. Which IOL formula do you recommend?
Not the SRK or Binkhorst. Older theretical formulas tend to overestimate the IOL power for short eyes, while SRK underestimates it. One of the newer-generation formulas should be used, as they are much more accurate with very long or very short eyes. Examples of newer formulas include the SRKII, SRK/T, and Holladay. These formulas are comparably accurate, though SRK II doesn’t do as well in very long eyes. Only the SRK II is simple enough to calculate by hand. It is the same as the normal SRK formula, but the A constant is modified for long or short eyes.
Note that in the example above, if the SRK formula had recommended and IOL power of +32 D, the SRK II formula tells you to use +32 +3 = +35D.
SRK/T (“T” stands for “theoretical”) and Holladay are complicated theoretical formulas refined by empiric observations. Many A scan units contain computer software that calculates recommended IOL power based on one of the newer formulas.

What is the disadvantage of a plano/ convex IOL design (implanted with the convex surface closer to the cornea)?
It has more spherical aberration. A plano / convex IOL has more spherical aberration than a biconvex design. A biconvex IOL with a rear surface power that is stronger than the front surface power causes the least spherical aberration.

Name an easy way to decrease the chance of making an errors in axial length measurement?
There are many potential source of error when measuring axial length and keratometry for IOL calculations. Measuring axial length in both eyes can decrease the chance of making a serious measurement error. If the two measurements are not close to equal, the measurement should be repeated.

A patient presents for preoperative evaluation for cataract surgery. The refraction in the catractous eye is – 9.50 sphere. She has been wearing a contact lens over that eye to correct the anisometropia. Keratometry readings in the eye are 43.00 /42.50. What is a potential source of error in the IOL power calculations in this case?
The contact lens must be removed a minimum of 2 hours before keratometry. Errors caused by molding of the cornea can amount to 1 D. Some clinicians recommend removing the contact lens 2 weeks before keratometry, but others say 2 hours is enough time.

Should emmetropia be the goal in all cataract surgery?
No. Induced anisometropia may produce intolerable aniseikonia as well as inducing heterotropias. Take into consideration the status of the other eye (aphakic versus pseudophakic) and the preoperative refraction of the patient. For example, a moderate myope may wish to remain so that she can continue to read without her glasses.

Lasik formula:
Actual K= [Average pre K-1.135
(Average pre K-Average post K)
Pre K1=43.0D Post K1=31.77D
K2=42.0D K2=30.92
Average= 42.5D Average=31.34
Actual K= [42.50D-1.135(42.50-31.34)
Actual K= [42.50D-1.135X11.16]
Actual K= [42.50D-12.66]
Actual K= 29.84D

MSC Optometry Question papers Yr1

2011-12-21T03:26:00.000-08:00

Assessing pupil reactions: RAPD

2011-12-08T05:09:00.001-08:00

Relative afferent pupillary defect (RAPD; Marcus Gunn pupil)
This is a test for optic nerve disease. In normal lighting conditions, the patient’s pupils appear normal. When a bright light is shone on to them, both pupils will contract. This is called a consensual pupil response.
Learn how to prepare for pupil assessment & recording your findings in a easy way

To carry out this test, arrange very dim lighting conditions and stand slightly to the side of the patient, so that they are not tempted to focus on you, but make sure that you have a good view of the pupils of both eyes. Ask the patient to ‘relax’ their eyes and pretend that they are looking across to the far side of a field. (You must ensure that the patient has ‘relaxed’ their focus, because as well as reacting to light, the pupils will also miose when their gaze is fixed on a near object.) When you are sure that the patient is ready, swing a strong light beam into the asymptomatic eye for a second or two. You will see the pupil constrict. Without moving the light beam, observe the affected eye. Because the neural pathways for the asymptomatic eye are functioning, the brain will pick up this impulse and will send a signal to the affected eye, warning it to contract. You can see this happen. Swing the torchlight slowly on to the affected eye, by dipping the beam below the patient's nose,

and then shining it into the affected eye. If the eye problem is with the neural pathway, the damaged pathway will transmit the signal less efficiently and the brain will sense less light entering the eye, so causing both pupils to dilate slightly to let in more light.

Remember that the resting pupil diameter is smaller in elderly people and the response in terms of maximum dilation is smaller (Bitsios et al., 1996), so elderly people are particularly difficult to examine. It is important to check for any RAPD prior to dilating a new patient’s pupils for examination.

Document that you have done this. If there is a gross problem, this is easy to identify, but sometimes the difference between the reactions in the two eyes is very subtle as mentioned above. You should double check any findings with a more experienced colleague until you are fully competent.

If you find an RAPD, speak to the ophthalmologist; he or she may wish to verify your finding of RAPD prior to the pupil being dilated, as this is potentially very significant to the diagnosis, particularly in optic nerve disease.

Pupils equal and reacting to light and accommodation (PERLA)

When you have checked that both pupils are equal, round and reacting to light, you must check the accommodation reflex. Put the room lights on. Sit directly in front of the patient so that you can observe the pupils of both eyes. Hold out your pen (or your finger) in front of both your noses, about 10 cm from the patient’s nose. Ask the patient to look at the pen for a few seconds, then into the distance, and then back at your pen. You should be able to see both eyes converging slightly for near vision, straightening up for distance, and converging again for near. Observe the pupils of both eyes simultaneously, and you should see the pupils of both eyes miose slightly, and equally for near vision. This is called the accommodative reflex. if everything is working correctly, you can writedown ‘PERLA’ on the patient’s notes.

Recording your findings

If everything is working correctly, you can write down ‘PERLA’ on the patient's notes. If there is

an RAPD, this is recorded as "RAPD’ (specify whether the right or left eye is affected).

The strabismus - Introduction

2011-11-06T17:22:00.000-08:00

The strabismus, a condition of lack of coordination between the two eyes is known and recognized since the earliest time. In the primitive folklore and mythology, it was considered to be an effect of evil eye.

The word strabismus was derived from the name of Greek Geographer named, ‘STRABO’ who had a horrible and unbecoming squint. The reorganistic and documentation of the condition of the squint in the literature dated back to 2600 BC. It was stated that Egyptian Goddess Maya Squinted and also Egyptian King D Joser (2600 BC) for whom the first pyramid was built, has gross internal squint, Guillemean described strabismus as a wrestling or within which drawn the sight unequally or a convulsion and pulling of muscles which move the eye or so same muscles of the eye are loosened and shortened, so the eyes as drawn downward, upward, to the right side or to the left side.

Hippocrates first noted the cross eye in children of cross eyes parents use of a mask with two holes in front of the eyes to straighten them was described by Paulus, Worth in 1903 classified the binocular vision in three grades and devised the four dot test. Maddox emphasized the treatment of abnormal retinal correspondence and Mary Maddox was first to organize the orthoptic clinic in London.

Routine eye Examination

2011-10-17T17:59:00.000-07:00

Introduction

For the majority of optometrists, routine eye examination is the activity that occupies most of their professional life.The workingday may be punctuated by contact lens appointments, dispensing or management, but “The Routine” is there like a heartbeat. It becomes an extension of the practitioner, and will eventually become as personal as a fingerprint.This is a desirable evolution, driven by the acquisition of knowledge and experience, but it does create problems for those starting out.The diversity of methods and interpretations encountered, even in undergraduate clinics, tends to create confusion rather than the wide breadth of useful variation intended.This is perhaps a controversial statement, but it is based on experience. The term “routine examination” becomes most familiar to optometrists as part of their professional qualifying examinations.

The term is used to describe the various procedures required during a full eye examination in order to properly assess both the optical status of a patient (and be able to prescribe an appropriate optical correction) and the ocular health. For the best part of a decade, the authors have been members of a team that was created to help optometric graduates through their pre-registration year and professional qualifying examinations (PQE).The job involved regular teaching in undergraduate clinics,as well as on postgraduate courses in preparation for the PQE. Experience as examiners for the College of Optometrists was also brought to bear, so over the years we have seen a lot of people go through university clinics, pre-registration year and their professional examinations.Initially,“Routine” gave us more headaches than any other section of the PQE and had traditionally the poorest first-time pass rate of any of the sections.We tried the usual refresher course approach, but it seemed to have no effect on the pass rate, though it did in other sections. It was only when we became more proactive that the results started to improve measurably.

Essentially we caught the pre-regs early in their year with a routine designed by a number of examiners, in an attempt to avoid some of the confusion that we were seeing in our tutees. The process involved one of us writing out an instruction manual which was then reviewed by a further ten examiners, who were between them teaching in all of the optometry departments then in existence.To everyone’s surprise we managed to settle all disputes without war breaking out. In fact, there really wasn’t that much that was controversial at all.The final version was then agreed and the result passed on to the graduate optometrists as they began their pre-registration year. It is from this work that much of this book has been developed, though it is hoped that it will prove as useful to a pre-registration optometrist as it may be to an experienced practitioner who, through years of developing a particular routine, may wish to revise a lesser used technique.Those entering the profession from university often have little reliable basis upon which to make informed choices, due to lack of contact with patients during their undergraduate period. Choices between different techniques during an eye examination become randomized, likely to be influenced more by ease of application or under the influence of one particular supervisor. What new practitioners need, we believe, is for experienced practitioners to take the responsibility of choosing a method that works, rather than a range that might or might not. As the new practitioner gains experience, they can begin to evolve their own routine, provided the roots are sound. The methods described are not the only ones, and maybe not even the best ones, but they have been thoroughly road-tested, both in the professional examinations and in practice. The authors have between them worked in every type of optometric practice from high street to hospital, and from locum to LASIK clinic, and these are the methods we have used.The book may prove particularly useful to those approaching the newly trialed pre-registration year, with its assessor visits and final examinations. The working environment is composed of legal, moral and

commercial elements. Guidance on what constitutes a proper examination has been provided by the College of Optometrists Code of Ethics and Guidance for Professional Conduct, which the General Optical Council tends to regard as the “peer view” in disciplinary cases. On the routine eye examination the guideline is as follows:

“The optometrist has a duty to carry out whatever tests are

necessary to determine the patient’s needs for vision care as to both

sight and health.The exact format and content will be determined by

both the practitioner’s professional judgment and the minimum legal

requirements”.

“(1) When a doctor or optician tests the sight of another person it shall be his duty

(a) to perform for the purpose of detecting sign of injury, disease or abnormality in the eye or elsewhere

(i) an examination of the external surface of the eye and its immediate vicinity

(ii) an intraocular examination, either by means of an ophthalmoscope or by such other means as the doctor or optician considers appropriate

(iii)such additional examinations as appear to the doctor or optician to be clinically necessary”

The essential message here is that if you test someone’s eyes with the aim of issuing a visual correction, you can’t just do a refraction.You have to screen the health of their eyes as well.This fact has shaped the structure of the routine as well as making its internal logic rather more difficult to follow at first.There are two end points rather than one and the efficient organization of the routine requires that both end points are arrived at with the minimum expenditure of effort and in a reasonable time. What constitutes a reasonable time is open to debate.At

undergraduate level, examinations are measured by the calendar rather than the clock, yet essentially the same ground is covered in 20 minutes in what is often rather disparagingly called “High Street practice”. Purists may sniff, yet the 20-minute sight test interval, which is the de facto industry standard, has not apparently caused widespread loss of sight among the population, and the remake rate has not gone into orbit. So it seems likely to stay.

In many smaller practices, 30 minutes is allowed between appointments, but that often includes 10 minutes for dispensing.

In larger practices, with dispensing a separate function, tonometry, fields and the use of autorefractors are often delegated to support staff. Provided that these staff are well trained, this can save considerable time. Either way, as a fully-fledged optometrist you may well have about 20 minutes maximum to carry out a “routine”. The other factor that needs to be taken into account is the patient. Research has indicated that they are unimpressed by prolonged sight testing. In fact, as will be discussed in Chapter 2, if the quality of the communication and the technique is good enough, the actual testing time bears little influence upon the patient’s satisfaction with their assessment, their recall of information, and their compliance with any instructions given. The routine can be regarded as a process of information gathering and decision-making and the fundamental difference between the undergraduate refraction and that performed by the fully-fledged practitioner is the approach to the gathering of information. Undergraduate refractions adopt what has been called a “database” approach.The less polite term for this is “box-filling”. Essentially, the same information is collected for every patient, whether it is directly relevant or not.The advantage of this approach in university clinics is that it is less likely that any essential information is missed or not recorded, so the supervisor will have enough information to make the clinical decision at the end of the clinic. Unfortunately, a drawback to this approach is that, for the student, information gathering and recording becomes an end in itself, and the crucial process of clinical decision-making becomes a delegated function. Furthermore, much of the information gathered will be essentially useless, which wastes time. If this approach was used extensively by experienced practitioners, the number of patients seen in a working day would be uneconomic and arguably less effective clinically. The experienced practitioner tends to have a smaller database to fill, though a certain amount of information is required for legal reasons, and some baseline information is useful to compare against future values (e.g. intraocular pressures, visual fields) for the early detection of trends.What was once “routine” may have become “subroutine”, brought in when the patient’s symptoms and history, or clinical findings, indicate their relevance. The more knowledge and experience the practitioner accumulates, the better this approach works. It follows that the routine is not fixed, it evolves. Not so many years ago, optometrists ascribed enormous significance to small differences in intraocular pressures and to the presence or absence of visual field changes, while largely ignoring the optic disc. Now we know that half of all glaucomas are normotensive, and that a patient can lose half of their nerve fiber layer without displaying a glaucomatous field loss, our approach to early glaucoma has changed significantly. It seems that optometrists will shortly be involved in the prescribing of therapeutic agents to treat a range of anterior eye conditions.The type of consultation needed to do this well is unlikely to be the same as one resulting in a pair of bifocals. For the moment, we shall concentrate on the more usual type of consultation, where the object is to arrive at a suitable optical correction, if required, and to screen the health of the eyes and adnexa.The precise order of the tests used will vary from practitioner to practitioner, and in many cases it makes little difference. However, there are some general principles to apply. Tests with the patient wearing their accustomed correction should be done before testing without it, in order to get an idea of their normal status before the testing process completely disrupts it.Tests should be done in such an order that each test makes subsequent ones easier. If you want to know what target to use for your cover test, it is helpful to know what the patient’s visual acuity is. If you are about to start retinoscopy, knowledge of

the symptoms and history and aided and unaided vision will help you to make a sensible choice of correcting lens, thus saving time. At the very least, they should not make the next test more difficult, or invalid. An example here would be to perform a fixation disparity test after a dissociation test (though this is frequently done), or to cover one up during the test and say “which line can you see now?” Binocular tests should precede ones that dissociate unless the reverse is unavoidable, and binocular vision should be stabilized before it is tested. Similarly, a patient with maculopathy should not be examined with an ophthalmoscope before all measurements of vision are completed, as the resultant after-image may take some time to clear. In most other cases, ophthalmoscopy can be done before or after the refraction. If done before, any pathological findings can be taken into account when you come to refract. Leaving ophthalmoscopy to the end allows refractive findings to point toward likely pathology, prevents a disabling after image, and allows the patient time to get used to the practitioner before the necessary invasion of personal space that accompanies ophthalmoscopy. But most of the time either way works just as well.

BINOCULAR ANAMOLIES, OCULAR & SYSTEMIC DISEASE

2011-10-12T16:10:00.000-07:00

BINOCULAR ANAMOLIES, OCULAR & SYSTEMIC DISEASE

Vinayaka Missions University,Directorate of Distance Education Salem India

MASTER OF SCIENCE IN OPTOMETRY

UNIT - 01

PATIENTS VISION PROBLEMS

STRABISMUS PATIENTS

ABNORMAL BINOCULAR VISION

CONSPICUOUS DEVIATION

PHORIA PATIENTS

OCULAR DISCOMFORT AND IMPAIRED PERFORMANCE

UNIT - 02

EVALUATION OF TREATMENT RESULTS

FACTORS THAT EFFECT PROGNOSIS FOR FUNCTIONAL CORRELATION OF STRABISMUS CONSTANCY OF STRABISMUS

UNIT - 03

ARC - AMBLYOPIA

ECCENTRIC FIXATION

SUPPRESSION AND SENSORY FUSION CONSTANCE

UNIT - 04

AGE OF ONSET AND DURATION OF STRABISMUS

FIXATION PREFERENCE

FAMILY HISTORY OF STRABISMUS

SIZE OF ANGLE OF DEVIATION

UNIT - 05

TREATMENT OF BINOCULAR ANOMALIES

OPTICAL CORRELATION OF AMERTROPIA

OPHTHALMIC PRISMS

UNIT - 06

OCCLUSION

VISION TRAINING

TREATMENT SEQUENCES FOR PHORIA

UNIT - 07

EYELIDS

CONJUNCTIVA

CORNEA

SCLERA

LACRIMAL APPARATUS

LENS

UVEA

RETINA

OPTIC NERVE

OVULOMOTOR NERVE

UNIT - 08

MOTILITY DISORDERS SECONDARY TO BRAIN STEM LESIONS

NYSTAGMUS

OCULAR MYOPATHY

UNIT - 09

GLAUCOMA

ORBIT

TUMORS

FOREIGN BODIES

CONTUSION

LACERATION

BURNS

BIRTH TRAUMA - AIDS

UNIT - 10

VISUALLY IMPAIRED CHILD

ASSESSMENT AND MANAGEMENT OF THE EXCEPTIONAL CHILD

UNIT - 11

MANAGEMENT OF APHAKIC NEONATE

OCULAR TRAUMA AND EMERGENCIES

COLOUR VISION

UNIT - 12

VISION SCREENING

LEARNING DISABILITIES

PERSPECTIVES ON READING DISABILITIES

DISPENSING, CONTACT LENS & VISION THERAPY

2011-10-12T15:39:00.000-07:00

Vinayaka Missions University,Directorate of Distance Education

Salem India

MASTER OF SCIENCE IN OPTOMETRY 1 Yr.

DISPENSING, CONTACT LENS & VISION THERAPY(2060202)

UNIT - 01

DIFFERENCES BETWEEN CHILDREN AND ADULTS - PHYSICAL DIFFERENCES - ACTIVITY DIFFERENCES - PSYCHOLOGICAL DIFFERENCES

UNIT - 02

OPHTHALMIC MATERIALS - FRAMES - PLASTIC - METAL - BRIDGE TYPES - TEMPLES -

HINGES - RIMLESS - FRAME SELECTION

UNIT - 03

STYLING - LENSES - MATERIALS - SINGLE VISION - MULTOFOCALS - SAFETY STANDARDS - SCRATCH - RESISTANT COATINGS - ANT REFLECTING COATINGS

UNIT - 04

ADJUSTMENT AND MODIFICATIONS - SCOPE - IMPORTANCE - INFANTS -ADJUSTMENTS

UNIT - 05

CONTACT LENS - REFRACTIVE APPLICATIONS - APHAKIA - MYOPIA - ASTIGMATISM -

ANISEIKONIA - ACCOMPDATIVE ESOTROPIA

UNIT - 06

PROSTHETIC APPLICATION - AMBLYOPIA - OCULAR DISFIGUREMENT - NYSTAGMUS -

ALBINISM AND ANIRIDIA

UNIT - 07

CLINICAL ASPECTS OF CONTACT LENS APPLICATION - POWER - CORNEAL CURVATURE AND BASE CURVE - CHOICE OF LENS - EVALUATION - LENS CARE PROCEDURE

UNIT - 08

VISION THERAPY FOR PRE SCHOOL CHILDREN - DIAGNOSIS - OLDER CHILDREN -

PRESCHOOL DIAGNOSIS

UNIT - 09

SIGN AND SYMPTOMS - SEQUENTIAL MANAGEMENT CONSIDERATION - VISION THERAPY

UNIT - 10

GENERAL CONSIDERATION - OCCLUSION - AMBLYOPIA - SUPPRESSION - ABNORMAL

CORRESPONDENCE

UNIT - 11

SENSORIMOTOR FUNCTION - DEFINITIONS - SCOPE - PERCEPTUAL AND HEARING

DYSFUNCTION

UNIT - 12

MANAGEMENT OF EXODEVIATINS - SCOPE - NATURE - MANAGEMENT OF

ESODEVIATIONS

MSC Optometry Syllabus of Vinayaka Mission University

2011-10-03T08:46:00.000-07:00

This are the syllabus for MSC Optometry under Vinayaka Mission University
Msc Optometry can be written under this university under distant education scheme

For more questions write to Optometrypro@gmail.com

1st year Syllabus

GROWTH AND DEVELOPMENT OF OPTICAL COMPOUND
DISPENSING, CONTACT LENS & VISION THERAPY
BINOCULAR ANOMALIES, OCULAR & SYSTEMIC DISEASE
LOW VISION AID
CLINICAL OPTOMETRY-I

2 nd year Syllabus

ORTHOPTICS
CLINICAL OPTOMETRY-II
CONTACT LENS
LOW VISION AID-II

Common abbreviations in contact lens practice

2011-09-11T07:14:00.000-07:00

Common abbreviations in contact lens practice

AEL Axial edge lift

AI Asymptomatic infiltrates

AIK Asymptomatic infiltrative keratitis

BOZD Back optic zone diameter

BOZR Back optic zone radius

BSR Back scleral radius

BSS Back scleral size

BUT Break up time

BVD Back vertex distance

BVP Back vertex power

CAB Cellulose acetate butyrate

CAEL Constant axial edge lift

CD Centre distance

CLAPC Contact lens associated papillary conjunctivitis

CLARE Contact lens acute red eye

CLIPC Contact lens induced papillary conjunctivitis

CLPU Contact lens peripheral ulcer

CLSLK Contact lens induced superior limbic keratoconjunctivitis

CN Centre near

CRT Corneal refractive therapy

D Displacement

Dk Oxygen permeability

Dk/t Oxygen transmissibility

e Eccentricity

EC Edge clearance

EOP Equivalent oxygen percentage

EW Extended wear

FDA Food and Drugs Authority

ff Flattening factor

FLOM Fenestrated lens for optic measurement

FOZD Front optic zone diameter

FVP Front vertex power

GPC Giant papillary conjunctivitis

HEMA Hydroxyethyl methacrylate

HGP Hard gas-permeable

HVID Horizontal visible iris diameter

IK Infiltrative keratitus

MDD Medical Devices Directive

MK Microbial keratitis

MPS Multipurpose solution

MRDT Minimum recommended disinfection time

NIBUT Non-invasive break-up time

OK Orthokeratology

p Corneal shape factor

PMMA Polymethyl methacrylate

POD Primary optic diameter

PRK Photorefractive keratectomy

PVP Polyvinyl pyrrolidone

REL Radial edge lift

RGP Rigid gas-permeable

RK Radial keratotomy

SEAL Superficial epithelial arcuate lesion

Si-Hy Silicone hydrogel

TBUT Tear break-up time

tc Centre thickness

TD Total diameter

te Edge thickness

TLT Tear layer thickness

TR Tear reservoir

USAN United States Adopted Name

BINOCULAR VISION ANOMALIES

2011-09-09T10:18:00.000-07:00

NATURE OF BINOCULAR VISION ANOMALIES

Introduction

Binocular vision is the coordination and integration of what is received from the two eyes separately into a single binocular percept.

Proper functioning of binocular vision without symptoms depends on a number of factors, which can be considered under three broad headings:

(1) The anatomy of the visual apparatus

(2) The motor system that coordinates movement of the eyes

(3) The sensory system through which the brain receives and integrates the two monocular signals.

Anomalies in any of these can cause difficulties in binocular vision, or even make it impossible. In considering the binocular difficulties of a particular patient, therefore, all three parts of the total system need to be investigated: